Optimization of thermosonication treatments to improve the quality parameters of posotia (Vitex negundo) juice

Abstract

In the current study, the influence of heat and thermosonication on the physico-chemical (cloudiness value, ascorbic acid content, pH, total soluble solid (TSS), titratable acidity (TA), and browning index (BI)), functional (total phenolic content (TPC), total flavonoid content (TFC) and antioxidant activity (AA)) and microbial (total plate count and yeast and mold count (YMC) characteristics of juice derived from leaves of posotia (Vitex negundo) was studied. Juices were thermosonicated using two different frequencies, namely 33 and 44 kHz with various time periods of 30, 45, and 60 min while maintaining treatment temperatures at 30, 40 and 50 °C. Treatment with heat and thermosonication (TS) did not result in any appreciable changes to pH, TSS, or TA. Increases in AA, TPC, TFC, cloud value, and browning index were seen after TS. However, the ascorbic acid level of posotia leaf juice was decreased after TS. The TPC, TFC, and antioxidant activity of the posotia leaf juice samples processed at 50 °C with 44 kHz frequency for 60 min, were found to be higher as compared with other TS conditions. The microbial populations in posotia juices were also significantly reduced by TS treatments. Microbes in juice samples were completely inactivated by thermal treatment, however there was also a noticeable reduction in quality indices. The findings of the study suggested that juices might be processed with TS without affecting the quality characteristics of posotia juices.